1 – Couples who work out are physically congruent.

It's all too common to see couples where one of the two is spindly legged, paunchy, and wearing a wife-beater T-shirt with so much splayed armpit hair sticking out that it looks like the kitty tail of a black angora cat stuck in a closed door... and that's the woman!

Meanwhile, her husband is trim and buff and well groomed.

Okay, maybe that much physical disparity is a bit of a rarity, but you see less extreme versions every day of couples that just don't fit.

People look at those couples with the same level of incredulity as when they see a lion and lamb palling around in some much-viewed YouTube video, only it's not nearly as cute.

I mean, you know that it's only a matter of time before the lion tears the lamb apart and gorges on its steaming entrails, or, alternately, leaves the lamb for a curvy fitness instructor who apparently bought the entire stock of those delightfully sheer see-through Lululemon yoga pants before they were pulled off the market.

No one says couples have to look alike to succeed in love, but physicality is sometimes a whole other category.

If one of you is fit and the other looks like a plate of overly warmed Camembert cheese, it says something about the latter's level of self-respect and level of regard for their partner. It matters.

2 – Sex, of course, is better for couples that work out.

You want a cure for a lackluster sex life, an inattentive spouse? Pick up a weight. Get thee to a gym.

When you're confident in your body, you want to get it naked and take it out for a spin. And people sense it, too. Even a-ni-mals strike curious poses, they feel the heat, the heat between me and you, or you and her, whatever the case may be.

And sex between people who work out isn't only more physical and sensual, it's more intensely visual. You leave the lights on during sex. In fact, you seek out special lighting equipment, preferably stuff left over from Gaga's last world tour.

You even get some high school kids to take time out from the thespian club's production of West Side Story to come over and man the lighting booms. Action!

Not only is sex better, it remains better for years. When your partner perpetually turns you on, it's just one more component of a good, satisfying relationship.

3 – Couples who work out are more likely to stay together.

Based on experiential evidence, couples need to share purposes in order to have any chance of sticking together.

All too often, ordinary couples, after the initial bloom of passion has worn off, start to see their sig other in the cold, harsh light of reality. They wonder what it was that they shared other than sex.

Too often that answer is "nothing," and in a panic, they have a child to rekindle the illusion of love, to give themselves an out from thinking or talking about their relationship.

In those cases, they'd have been better off buying themselves an Xbox, because at least that's something they might actually do together. Besides, not really loving each other probably won't affect the Xbox's internal development very much.

Couples who work out, though, have at least one shared purpose, and that's taking mutual interest and maybe even delight in the care, building, and maintenance of their bodies, and when they have a kid, it's for the right reason – love, and maybe to have someone to watch the dog while they go work out.

4 – Food is no longer a source of contention for couples that work out.

You know why cats and dogs don't get married? Because it just doesn't work when you fill one half of the grocery cart with Purina Cat Chow and the other with Hungry Dog brand deep-fried liver snaps.

Making two entirely different meals with different macronutrient profiles for dinner isn't a recipe for harmony or health. The same goes for going out to eat. When one of you is body conscious and the other isn't, there's tension and disharmony.

If one of you wants to eat at "The Hungry Heifer" and the other wants to eat at the "Kumquat and Fowl Organic Bistro," it leads to friction, fighting, and possibly, depending on who wins the argument, fatness.

That's not true of couples that work out. They're of like minds and like guts. Eating is something they do because they want to give the body what it needs. Food isn't a substitute for an inattentive spouse, a lousy sex life, or boredom with life in general.

5 – Couples who work out don't argue about where to go on vacations.

The vacation choices of people who don't work out are pretty predictable. The guy wants to go to Vegas to play craps, or maybe Canton, Ohio to visit the Football Hall of Fame.

Chances are the wife wants to spend their only two weeks off from work visiting her parents in some giant, flying-cockroach infested retirement city in Florida that's a hundred miles from the ocean. That, or maybe she wants to go see the giant butter cow at the Iowa state fair.

But if you both work out, it's a done deal. You both want to go to the Bahamas or Hawaii; anywhere you can strip down to your swimsuits or trunks and show off those glistening bodies.

Hell, you both figure that there will be plenty of time to go to Paris, take a cruise around the world, or even see that giant butter cow when you're really old, physically unappealing, and have no desire to shed your clothes for each other, let alone the world.

6 – Couples who work out spend more time together.

If one partner works out and the other doesn't, guilt and/or resentment invariably ensues. She's mad because you're at the gym "all the time" instead of at home scrap booking with her.

She's hesitant to set up any social engagements because she doesn't know if it'll conflict with your gym time.

Besides, when the Petersons invite you for dinner, they seemingly coat everything with cheese and bear lard and they guilt you into eating five kinds of dessert and your husband spends half the meal shooting daggers at you with his eyes because he doesn't eat that kind of stuff.

But if both of you work out, you're spending time together. You don't even have to have her as a training partner because, at any time, you can look up and catch a glimpse of her fine, toned butt, like a homing signal, calling out to you on the glute ham raise and it makes your heart feel glad.

Furthermore, you celebrate each other's accomplishments and personal records. You get to serve as each other's coach. You've got a guaranteed spotter, one whom you trust not to be distracted when some quivering mammal in a sports bra walks by.

You keep each other in check, physique wise. You don't slip up because she doesn't slip up. And when you do slip up, it's together, and playing hooky from school always was a lot more fun when someone did it with you.

7 – Buying presents for each other is easy for couples that work out.

Guys are generally horrible at buying presents, and women, while they try hard, invariably buy the wrong things for their husbands.

Most of the time, in an act of last-minute desperation, the guy will end up buying her some tiny, chipped off fragment of diamond dust glued to a pendant from some strip mall jeweler that ended up costing two week's salary.

And the well-intentioned wife will buy her husband the Battlestar Gallactica flight suit he wanted, only it's the cheesy one from the original series instead of the remake. Talk about heartbreak!

But, if you both work out, you don't have to agonize over whether she'll like the red sweater that depicts different species of dinosaurs. You can buy her workout tops, yoga pants, gloves, foam rollers, even a Prowler, and you can't go wrong.

Hell, even racy panties are never an inappropriate gift for a girl who works out because unlike her non-working out counterparts, she truly appreciates decorating her ass and body, just as the non-workout woman appreciates decorations for the house like drapes or lace doilies for the sofa.

The same approach works for the guy. Any piece of workout equipment will do nicely, as will clothes that enhance his buffitudiness.

8 – Couples who work out get more done.

When both of you work out, the notion that one of you is a weak little daffodil that'd best stay in the kitchen making Rice Krispie treats goes by the wayside. Women who work out are imminently functional; they are as capable as men when it comes to doing physical labor.

Most guys, when they need to move a couch, unload a truck, or move a concrete bird feeder, have to wait for their smarmy neighbor to get home so they can ask him to help. That, or you have to hire two beefy college kids that track dirt all over your house in the process. Not so with a spouse who works out.

Move a couch? Unload sheet rock? Move a pallet of concrete garden gnomes? Shee-it, you don't need to two men to move you, you've got Brittany, your own personal stevedore who can out squat, out bench, and out lift your cheesy neighbor.

9 – Couples who work out have fewer arguments.

When you both work out, you tend to release your frustrations in a healthy way.

So the boss bitched at your spouse, you lost the Petersen account, a homeless person barfed on her Jimmy Choos, and selling extended warranties for in-window air conditioners isn't as thrilling a career as you both thought it might be.

But if you both work out, she doesn't get bitchy, you don't deflect any attempts to find out what's wrong with a grunt, and you don't take her lovingly prepared Swedish meatballs and start angrily pelting them at any car that's driving by playing that stupid "Happy" song on its radio.

Instead, you've both gone to the gym and treated some weights rudely.

You come home calm, collected, happy even, and ready for some sex under the strobe lights.